Switchboard systems



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TESTING APPARATUS FOR MULTIPLEISWITGHBOARDYSYSTEMS. A A. No. 496,907. Patented May 9 1893 (No Model.)

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TESTING APPARATUS FOR MULTIPLE SWITOHBOARD SYSTEMS.

No. 496,907. Patented Ma 9, 1893.

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME PLACE. Y

TESTING APPARATUS FOR MULTIPLE-SWITCHBOARD SYSTEMS.

SPECIFICATION forming part of Letters Patent No. 496,907, dated May 9, 1893.

Application filed March 24, 1890.

To aZZ whom it may concern.-

Beit known that I, CHARLES E. SCRIBNER, a citizen of the United States, residing at- Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Testing Apparatus for Multiple-Switchboard Systems, (Case No. 224,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

The object of my invention is to provide ready means of doing the operators work at the telephone exchange office of a multiple switch board system.

The features of my invention may be stated as consisting- First. The telephone lines are arranged so that when connected in metallic circuit through the central office the different limbs of the two circuits will be reciprocally united, one with another, that is to say, the limb of one circuit which includes the springs and contacts of its switches will be connected with that limb of the other circuit which connects with the test pieces of its switches in order that theilines may test busy when thus connected together, although the subscribers may have hung up their telephones.

Second. The telephone lines are connected in metallic circuit with the different switch boards, the limb of each circuit which connects with the springs and test pieces being normally grounded through the subscribers bell, that is, when the subscribers telephone is'hung up, and the other limb being normally open at the subscribers station, the limb which is normally grounded being permanently connected through the high resistance individual annunciator of the line at the central oflice. Each line is provided with a terminal loop plug and cord and a cord switch and a listening and calling key and the sleeve of the plug is connected with that limb of its telephone line which passes through the springs and contacts of the switches thereof Serial No. 345,039. (No model.)

connecting with the sleeve of the plug will be connected with the test portion-of the other line while the test portion of the first line which is connected to the tip of the plug will 5 5 be connected through the medium of the tip of the plug with the limb of the other line which extends to the spring of the switch in which the plug has been inserted.

Third. When airlines are used of moderate length so that their capacity is only moderate the loop plug of a line may be used in testing another line; when, however, the circuits are of considerable length and run in cables making their condenser capacity considerable I preferably use a special test plug connected in a circuit leading to ground through a buzzer and battery so arranged that a line when tested will be charged by the battery and buzzer without causing a click in the operators telephone connected in circuit with the buzzer. The loop plugs may always be employed in making a test required; in case the lines tested are of high capacity one or two taps or applications of the tip of the plug to the test piece will charge the line, the sounds caused in the telephone at such times being 'disr'e garded.

Fourth. In connecting the test rings of'connected lines with ground to make them test test rings to the limb connecting through the annunciator to ground'w'hen the telephones are off the hook and through the subscribers outfits to ground when the telephones are on the hook.

My invention will be readily understood by reference 'to the accompanying drawings, in which V Figure 1 is adiagramillustrative of the circuits of three telephone lines connected with three switch boards with the operatorsoutfits at two of the boards,.the subscribers apparatus at one station only being illustrated in detail. Fig. 2 is an illustrative diagram of two connected lines, the telephones of the stations being hung up with testing apparatus applied to a test piece of one of the lines. Fig. 3 is a plan viewof two listening and calling keys mounted upon the same strip. Fig. 4 is a side elevation thereof.

'The listening and calling key as shown in Figs. 3 and 4 consists in cord or line contacts a b, the telephone springs c d, the plunger 6, the spring f carrying the guide on which the plunger is mounted, the contact g against which springf normally rests and the gener- I ator contact it against which spring f is closed when the handle of the plunger is depressed. When the plunger is forced in between-springs c d these telephone springs c (1 will be disconnected from the line contacts a I) respectively, the tension of these springs c at being such that when the plunger is withdrawn these springs c (1 will rest upon said contacts a b. By simply pressingdown upon the handle of the plunger the springf will be separated from its contact 9 and closed upon generator contact 72.. Such a listening and calling key having been described and claimed in a prior application forms no part of my invention herein, except as used in connection with the special circuits herein shown.

Telephone line 1' extends in two limbs or branches t" i to the central office, limb i being connected through the spring and contact of each of the switches t i 2' asshown in Fig. 1, and from the contact of the switch 2' on the last board to contact 2' of the cord switch and thence when the plug of the cord switch is removed from its socket to contact 71 of the cord switch and thence to the strand i of the cord, said strand 11 being connected with the sleeve of the plug. It should be observed that the contact t of the cord switch is provided with a'connection to the telephone contact I) and spring (I of the listening and calling key. A ground branch t is permanently connected with the limb t" and in this branch Wis permanently included the subscribers individual annunciator 2' this individual annunciator is constructed to act as a retardation coil and should be of high resistance, say six hundred ohms. The other limb t which is the test portionor limb of the circuit will be normally open both at thesubscribers station and at the central office; a branch 7c from this limb i extends to the strand of the cord connecting with-the tip thereof; this branch including in its circuit the springf and contact gand being provided with a connection through springs 10' k to the contact a of the listening and calling key.

The subscribers outfitis of usual construction consisting of a bell and generator in a ground branch normally closed to limb 'L" as will be shown at station 1, Fig. 1, when the telephone is on the switch, the limb 2' being then open; on removing the telephone from the switch the ground branch containing the bell and generator is opened as shown at said stationland the limbs t 2' united in metallic circuit through the subscribers telephone. The telephone circuit Z of sub-station 2 eX- tends in a similar manner by limbs Z Z to the switches Z Z Z, the individual annunciator Z being included in a ground branch Z The subscribers outfit at board 2 and the connections of line Z with its cord switch and listening and calling'key are not shown. Sub-station 3 is connected by circuit m in the same manner by limbs m and m with switches m m m and at board 3 with its individual annunciatorm 'in ground branch m cord switch, plug and listening and calling key being of the construction described with respect to line t'.

I have shown in connection with the subscribers outfit at each of the boards 1 and 3 a test plug forming the terminal of a ground branch including a connection with the operators telephone and a battery, together with a buzzer or rheotome. Thus as shown at board 3 the plug it is connected with the flexible cord 7t. and thence through one coil n of the converter and thence through the contacts of the rheotome n and thence through battery 12 to ground. The other coiln of the converter is included in the local circuit of the telephone, this being a convenient and well known way of connecting a test circuit with an operators telephone. A battery 0 may be included also in the local circuit of the telephone, this local battery serving as a test battery when the loop plug of a line is used in making a test, the central oflice ground for this test battery 0 when such test is made being formed through the ground connection of the individual annunciator of the line whose plug is used in making the test.

Suppose now that telephone line i is in its normal condition, that is, the telephone of station 1 on the switch and the limb '6 open at both ends; in such case the condenser capacity of said limb 1 will depend upon certain well known conditions, that is to say, upon its length and distance from theground;

it run in a cable for a considerable distance its capacity would be such that it" a branch containing a battery and telephone is'connected therewith the current from the bat tery in charging the line might cause a click in the telephone, if, however, the limb i is an air line of moderate length its condenser capacity may be disregarded as it'w'ill. not be sufficient to cause a flow of current sufficient to produce a click or sound in the telephone. Now when one telephone line isconnected with another at the central office there will:

be an intersection of the circuits; thus terminal loop plug 9 of line m is shown inserted in spring jack switch 2' Now the limb m'of line m being connected with the sleeve of,

said plugp and the limb m being connected with the tip thereof it follows that the united circuit of the two telephone lines'th us formed will resultin the circuits intersecting each other, that is to say, the limb m of line m will I be connected with limb i of line 2', while limb m of line m will be connected with limb i" of line i. The connection of limb i'with individual annunciator 2' will be broken at switch 2' while the individual annunciator m of line m will be left in its ground branch m to serve as a clearing out annunciator. By this arrangenient of the circuits when two lines are connected together the test portion ofoneline will be connectedto the spring portion of-the other line and thence to the subscribersstation and either through his outfit to groundor through his return line to thecentral Mice and through his annunciator to ground. That is to say, suppose both subscribers thus connected, that is, subscribers 1' and 3 should hang up their telephonesso as to open the outer ends'of limbs 17 m it will beobservedd This limb 11 being connected with limb m the test battery in the test circuit will find the circuit over limb m to ground at station 3. In case the loop plug, as for example plug p of line m,be used in making the test the test circuit will be from the ground branch including the annunciator, that is, branch m through the annunciatorm to branch m and thence through the contacts p p of the cord switchand thence to the contact b and spring 01 of the listening keyand thence through the batteryo and the telephone to spring 0 of the listening key and thence to contact a and thence through the springs 10 p and thence through contacts 9 f of the calling key to the strand 10 of the cord of plug 1), said strand 19 being connected with the tip thereof. Now by'tapping the plug 19 a few times to the test piece of any line and listening at the telephone included in the circuit thereof it may be determined whether the line is in use, no matter whether the line be of high capacity or low capacity, for upon so tapping the test piece, if the test piece be connected with ground, it will be evident by the series of clicks which the operator will hear in her telephone; if it is not connected with ground, although the operator may hear one or two clicks as the line charges, the third touch will give no sound in her telephone. The test piece, as before stated, will always be grounded when it is connected with another line either through a subscribers set to ground or through a clearing out annunciator to ground. By using the special test plug n, however,.in the battery circuit of which is included the rheotome and telephone, any false signal in the telephone will be prevented as the test will be a tone or buzz for a busy line and the absence of tone or buzz for a line that is not busy, and although the operator may hear a click as she touches the special test plug to a test ring there will be no tone in her telephone.

Suppose subscriber of station 3 wishes connection with subscriber of station 1; he first operates his generator there by throwing down annunciator m the operator at board 3seeing the shutter fall raises plug 10, bringing her telephone into circuit; she then makes the test either by means of said plug 19 or by plug it as may be most convenient. The test will be madeby touching the tip of the plug, whicheveris used, tothe test piece of switch 4? of line We will suppose first that plug p is used and of course the plunger of the listening key will be out so that the, spring 0 will rest on contact a and spring (2 upon contact b. The circuit thus formed will be from ground by branch m to limb m and thence through contact 10' p of the cord switch to contact I) and spring at of the listening key andthence through battery 0 and the operators telephone to spring 0 and contact a and thence by springs 19 p of the cord switch'to contact gand springf of the calling key and thence to strand p of the cord of plug p, said strand p connecting with the tip thereof. Now if the line i is free the test piece of switch 2'? will be disconnected from ground and hence the circuit of battery 0 will be opened at the test or return portion 2'. The operator therefore hearing no click in her telephone will know that the line 2' is free and will thereupon insert the plug 1) into switch 71 as shown. Depressing the handle of the calling, key sends generator current over limb i to ring the subscribersbell at station 1; the subscriber at station 1 will thereupon take down his telephone and the two subscribers will be connected as shown in Figs. 1 and 2. The plunger of the listening key will be inserted as shown between springs c d to disconnect the telephone and the annunciator m will be left in a ground branch to serve as a clearing out signal device. Suppose, however, the condenser capacity of limb were considerable then it would be desirable to use the special test plug n in connection with the rheotome and battery n; if on applying tip of plug '17, to the test piece of switch '6 a tone is heard in the telephone of the operator it will be notice that the limb i is provided with a ground connection, that is, that the line i is busy;-if, however, no tone is heard it will be notice that the line is free and the operator will proceed to make the connection by inserting plug 19 as before described.

In casethe special test plug as n be relied upon in making the test it will not be necessary to include a battery 0 in the circuit of the operators telephone.

My invention admits of various modifications which would readily suggest themselves to those skilled in the art and I therefore do not limit myself to the details of construcclaimed in my application, Serial No.339,597,

filed February 7, 1.890, for multiple switch board apparatus. I therefore limit my patent in this case to the combinations hereinafter set forth.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- 1. Two telephone lines connected in metallic circuit through the central ofitice, the different limbs of the two circuits being reciprocally united one with another, that is, the return or test limb of each being united at the central office with the opposite limb of the other, a ground branch including an individual annunciator of high resistance constructed to act as a retardation coil, in combination with the switches at the subscribers station, whereby on hanging up the telephone the return portions of said telephone lines will be grounded respectively at the subscribers station of the other line, substantially as and for the purpose specified.

2. A telephone line provided at the subscribers station thereof with a switch op erated by the telephone, a normally closed ground branch including the bell and generator said line extending in two branches to switches on different switch boards, the branch which is normally grounded at the subscribers station being provided with a permanently closed ground branchincluding an individual annunciator at the central office, in combination with a terminal loop plug and cord for said line, a cord switch and a listening and calling key and the operators telephone, substantially as and for the purpose specified.

3. The combination with telephone lines connected in metallic circuit with the different switch boards, the limbs of each circuit which connect with the springs being grounded through the subscribers bell when the subscribers telephone is hung upon the switch and the other limb being normally open at the subscribers station, of a different ground branch for each line including the individual annunciator thereof, the terminal loop plug and cord, the cord switch and listening and calling key of each line, the sleeve of theterminal plug of each line being connected with that limb of its telephone line which passes through the springs and contacts of the switches thereof, whereby when one line is connected with another by insertion of the loop plug into a switch of the other the opposite corresponding limbs of the two circuits will be reciprocally connected together, substantially as and for the purpose specified.

4. The loop terminal plug of a telephone line and its cord, the strand of the cord connecting with the tip thereof being provided with a connection through a battery, the 0perators telephone and a ground branch including the high resistance individual annunciator of the line, in combination with the test portion of a line to be tested, said test portion being either open or grounded accordingly as the line is free or busy,su'bstantially as and for the purpose specified.

In witness whereof I hereunto subscribe my name this 25th dayof February, A. D. 1890.

CHARLES E. SCRIBNER.

Witnesses: V

ELLA EDLER, GEORGE P. BARTON, 

